The present invention relates to cooperating slidable aluminum alloy members, and more particularly, to an improvement in first and second slidable aluminum alloy members that slide relative to each other and in which a sliding portion of the first slidable aluminum alloy member is comprised a fiber-reinforced aluminum alloy.
Cooperating slidable members of this kind can be represented, for example, by the combination of a cylinder block of an internal combustion engine and a piston that is slidably fitted in a cylinder bore of the cylinder block. According to the prior art, a particulr region on the inner wall of the cylinder bore includes a single kind of fiber for reinforcement in an aluminum alloy matrix (see, for example, Japanese Patent Laid-Open No. 182338/1985).
It is desired that the inner wall of the cylinder bore has at least a predetermined strength as well as self-lubricating ability to obtain good sliding properties under the conditions where the circulating oil lubrication is not sufficiently effected, such as at the time of starting the engine. However, use of a single kind of fiber for reinforcement is not sufficient to properly meet such requirements.
When an alumina fiber is selected as a reinforcement fiber, furthermore, the alpha rate of the alumina fiber so seriously affects the strength and hardness of the fiber that the alpha rate must be set to a suitable value. When the volume content of the alumina fiber is not appropriate, even if the alumina fiber has an appropriate strength, the inner wall of the cylinder bore is not sufficiently reinforced with that fiber thereby causing an increase in the amount of wear in the inner wall of the cylinder bore and the piston.
Both of the slidable surfaces of the cylinder block and piston comprised an aluminum alloy are of the same material, and if means are not provided between the surfaces for preventing adhering and seizure between them, there is a risk that the two relatively sliding portions will adhere when the members are stationary thereby inhibiting relative sliding motion when needed, such as upon starting the engine, particularly due to lack of lubrication between the members as a result of the engine being stopped for awhile. In addition, it is also possible that a seizure will occur between the two members during operation.
The above-mentioned problems can be caused not only in internal combustion engines but between any two sliding members that slide relative to each other during operation such as in a compressor, an automatic transmission, or a like unit.